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Microsoft Security Bulletin MS02-071: Flaw in Windows WM_TIMER Message Handling Could Enable Privilege Elevation (328310)
From: "Microsoft" <0_44009_04BF067D-4CF8-4245-B5C1-58573E5746A8_US () Newsletters Microsoft com>
Date: Fri, 7 Feb 2003 18:32:55 -0800
-----BEGIN PGP SIGNED MESSAGE----- - ---------------------------------------------------------------------- Title: Flaw in Windows WM_TIMER Message Handling Could Enable Privilege Elevation (328310) Released: 11 December 2002 Revised: 07 February 2003 (version 2.0) Software: Microsoft Windows NT 4.0 Microsoft Windows NT 4.0, Terminal Server Edition Microsoft Windows 2000 Microsoft Windows XP Impact: Privilege elevation Max Risk: Important Bulletin: MS02-071 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS02-071.asp http://www.microsoft.com/security/security_bulletins/ms02-071.asp - ---------------------------------------------------------------------- Reason for Revision: ==================== Subsequent to the release of this bulletin it was determined that the patch for Microsoft Windows NT 4.0 machines introduced an error that could, under certain configurations, cause NT 4.0 to fail. Microsoft has investigated this issue and is releasing an updated patch for Windows NT 4.0. The bulletin has been updated to include the new download links for the NT 4.0 patch. Customers who have installed the patch on Microsoft Windows 2000 and Windows XP are unaffected by this error. Issue: ====== Windows messages provide a way for interactive processes to react to user events (e.g., keystrokes or mouse movements) and communicate with other interactive processes. One such message, WM_TIMER, is sent at the expiration of a timer, and can be used to cause a process to execute a timer callback function. A security vulnerability results because it's possible for one process in the interactive desktop to use a WM_TIMER message to cause another process to execute a callback function at the address of its choice, even if the second process did not set a timer. If that second process had higher privileges than the first, this would provide the first process with a way of exercising them. By default, several of the processes running in the interactive desktop do so with LocalSystem privileges. As a result, an attacker who had the ability to log onto a system interactively could potentially run a program that would levy a WM_TIMER request upon such a process, causing it to take any action the attacker specified. This would give the attacker complete control over the system. In addition to addressing this vulnerability, the patch also makes changes to several processes that run on the interactive desktop with high privileges. Although none of these would, in the absence of the TM_TIMER vulnerability, enable an attacker to gain privileges on the system, we have included them in the patch to make the services more robust. Mitigating Factors: ==================== - An attacker would need valid logon credentials to exploit the vulnerability. It could not be exploited remotely. - Properly secured servers would be at little risk from this vulnerability. Standard best practices recommend only allowing trusted administrators to log onto such systems interactively; without such privileges, an attacker could not exploit the vulnerability. Risk Rating: ============ - Important Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletins at http://www.microsoft.com/technet/security/bulletin/ms02-071.asp http://www.microsoft.com/security/security_bulletins/ms02-071.asp for information on obtaining this patch. - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 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- Microsoft Security Bulletin MS02-071: Flaw in Windows WM_TIMER Message Handling Could Enable Privilege Elevation (328310) Microsoft (Feb 07)